Frame Relay - for Faster and More Efficient Data Communications ...

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42Table 2Relationship between Functional and InformationModelFunctional Model,see Fig. 6Managed Objects in InformationModel, see Fig. 18TransportFunctionTrailConnectionTrail (Managed Object)Connection (Managed Object)TransportReferencePointsEnd point of trail APEnd point of a connection CPor network connection TCPTrail Termination Point TTP(Managed Object)Connection Termination Point CTP(Managed Object)Fig. 12Functional Model of PDH muldex and line systemDS1D1PHTFramed 2 Mbit/s signalHDB-3 coded 2 Mbit s signalPhysical Media TrailRelationshipsbetweenTransportReferencePointsand relatedManagedObjectsOne-to-one relationshipbetween AP and CPOne-to-one relationshipbetween CP/TCP and CPOne-to-n relationshipbetween AP in a serverlayer and CP in aclient layerOne-to-one relationshipbetween TTP and CTPexpressed by connectivitypointersOne-to-one relationshipbetween CTP and CTPexpressed by connectivity pointersOne-ton relationshipbetween I l P in a server layerand CTP in a client layerexpressed by namingClient-to-server AdaptationTrail TerminationERICSSON REVIEW No. 1-2, 1992
43layers, Table 1. Each function is characterisedby a number, which appears in tablesand figures in a consistent way. (Thesame number is used for the send and receiveparts).The example in Fig. 12 is based on the examplein Fig. 11 and shows the connectionof the terminals via a line system consistingof line terminals and one regenerator.Thirty 64 kbit/s Circuit Trails are transmittedvia a DS1 Trail which consists ofTrail Terminations, two Sub-Network Connections(TCP-CP) and one Link Connection(CP-CP) in the Path Layer network.These Sub-Network and Link Connectionsare served by three D1 Trails in the SignalLayer network. The D1 Trail in the middleconsists of Trail Terminations and two LinkConnections.The D1 Trail is served by two PhysicalTrails, i.e. two cable sections separated bya regenerator in the physical layer.Fig. 13 shows the Functional Model of adigital multiplexer converting 64x2 Mbit/ssignals into one 140 Mbit/s signal. Terminala is connected to a digital multiplexera, and the multiplexer is connected to a140 Mbit/s line terminal a. Similarly, thecorresponding b-side contains line terminalb, digital multiplexer b and terminal b.The multiplexers and line terminals containresources for management. TransportFunctions 1 to 4 are explained in Table 1and functions 10 to 19 in Table 3.Synchronous Digital Hierarchy (SDH)The functions of SDH systems, as definedin CCITT Recommendations G.781, 782and 783 for digital multiplexers and for digitalcross connects, are much more complicatedthan PDH systems that conformto existing Series G Recommendations (-Blue Book). This is compensated by the increasedflexibility and manageability ofSDH systems, however. Ample overheadinformation, the corresponding resourcesand management interfaces suitable forFig. 13Functional Model of PDH multiplexer (64x2 Mbit/sto 140 Mbit/s)ERICSSON REVIEW No. 1-2, 1992
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